Some say that if you as a buyer deal directly with the agent that has listed the home you are interested in, you may not be able to guarantee that the agent has your best interest at heart. The only way to guarantee that is to actually to hire a "buyer's" agent who will get a percentage of the selling price usually from the seller. That agent will look out for your best interest.
And even then, to play it safe, never tell anyone how high you are willing to go. If you decide to deal directly with the listing agent, never tell him or her how high you are willing to go on the house. If the seller's real estate agent has a fiduciary responsibility to the seller, they WILL tell the seller everything you say, so pretend you are under police interrogation.
Just give them the price you want to pay for the house and if they ask how high you are willing to go, tell them that's it. If the seller does not agree with your offer s/he may make a counter-offer and that may start a back and forth negotiation process where both parties will come to a mutual agreement.
Good luck to you!